1. Field of the Invention
The present invention pertains to image data management and in particular to a method of organizing and storing imagery and metadata from a collection of Wide Area Motion Imagery (WAMI) frames into an Object Storage Device (OSD) and a method of retrieving tile objects that intersect with an Area of Interest (AOI) from a WAMI frame within a collection of WAMI frames that are stored on an OSD.
2. Discussion of Related Art
An image generally contains a plurality of pixels (e.g., several hundred megapixels) and each pixel has one, two or more bands. Each band has a certain color depth or bit depth. For example, an RGB color-based image has 3 bands, the red band (R), the green band (G) and the blue band (B). Each of the R, G and B bands can have a depth of 8 bits or more.
An image sensor can be used to capture a series of images, each image having several hundred megapixels. The images may be captured in sequence, for example at a reasonably constant frequency or rate. Each image (i.e., each still image) in the sequence or series of images may have one or more distinct bands and may cover any part of the electromagnetic spectrum that can be captured by the image sensor. The image sensor may be a single sensor or a combination of a matrix of multiple sensors arranged to generate a single image. Therefore, the series of relatively large images captured by an image sensor over a certain period of time at a near constant capture rate are considered to be large format motion imagery or WAMI.
An image detector may be comprised of multiple image sensors arranged in some configuration, such as, for example, a matrix. Each image sensor in the multiple image sensors can produce a separate image at a substantially same instant in time. Thus, for an instant in time, a notionally single region captured by such a sensor can include several images captured by the multiple sensors. These several images can be combined to generate a single large mosaic image of the area covered by all the sensors for that instant in time. These several images can also be considered to be a large format motion imagery frame or a WAMI frame.
The image output by the image sensor or detector may be ortho-rectified or ground corrected to generate a map, which is also an image. The original or first image (i.e., WAMI frame) captured and output by the image sensor may be optionally converted into a sequence of progressively smaller images. Each subsequent image in the sequence is smaller than the previous image in the sequence. The progressively smaller images are referred to as R-sets, reduced resolution datasets (RRDs). An ortho-rectified WAMI frame comprises the original or first image (WAMI frame) and a sequence of zero or more R-set images.
The term ortho-rectified, in the present context, may be used interchangeably with the terms geo-rectified, planar-rectified and geo-corrected. The term ortho-rectified, in the present context, refers to an image that allows a form of per-pixel spatial reference (e.g., geospatial reference). An ortho-rectified image is an image that is corrected so that the scale in the image is uniform such that distances shown are uniform and can be measured like a map. Orthorectification is the process of removing the effects of image perspective (e.g., tilt) and relief effects for the purpose of creating a planimetrically correct image. The resultant orthorectified image has a constant scale wherein features are represented in their “true” positions.
The ortho-rectified image maybe stored in a known or proprietary file format. The format may contain a header which is a computer data structure that describes various parameters of the image, as well as may hold additional metadata about the image, for example, time of acquisition, information about the capturing device, geographic reference data, access rights, and copyright information, etc.
An object storage device (OSD) is a conventional computer data storage method wherein a collection of bytes, referred to as data, is stored on the OSD as objects. Each object is assigned a globally unique Object Identifier (OID). An OSD is different from a Traditional File System that stores data as files in a hierarchy of folders on a block-based storage device.